Laguna 1.9 dTI ...more woes

Strange one this- if it suddenly started without warning and its not using coolant, or producing slime in the header tank...

Firstly get a thermometer and ram it in the header tank with the gauge at different degrees of heat and see exactly wot temperature the beast is running at.

With the gauge at 3/4 the fan should be on, is it?

Probably not.

No- because they silt up over time, not overnight!

most likely

No.

No.

Would overheat at all times and take awhile to cool off again after being too hot. I have seen the impellors fall off thoough, so if the thermostat and radiator check out- its off with the pump.

The fact that this problem has just suddenly appeared, does suggest theory no.3 is the first port of call.

My dad has a 2.0 DTI Vectra and that suffered from a power/overheating problem last year under mfr warranty. He said it was the MAF they replaced. It seem bizarre to me, but some kind of ECU fault create a temperature prob?

I'd add to check the system is maintaining the proper pressure. Expansion tank cap seal gone can cause this sort of problem.

Dave Baker - Puma Race Engines

"There's no sign of any leakage"

Fan switch failures seem common in many makes of car, due to their environment I suppose. The switch is usually bolted into the radiator AFAIK. Leaving the car idling in the garage/drive for a few minutes should generally warm it up enough for the fan to start.

Also there may be an airlock in the cooling system - on my Laguna I squeezed the top radiator-to-engine hose and air bubbled out through the expansion tank - there may be a more scientific way of doing this!

A leaky seal on the expansion tank cap has been mentioned, and I can add a cracked expansion tank to the list (with a small jet of high pressure boiling coolant spraying over the battery! A trip to the local scrapyard and a fiver later it was sorted). Bloody Renaults etc. :o)

Fair enough, but a pressure test on the cooling system can tell you a lot. If the pressure drops with no sign of external leakage, then water is being lost inside the engine.

HTH

Anthony Remove eight from email to reply.

I've checked daily since Sunday. The water level has not dropped. I've also squeezed the radiator return pipe this afternoon after my tretcherous trip home on the M62. It didn't make any big bubbles surface in the exp. tank. I might check tomorrow whether there's any significant heat coming off the return pipe after I've had my trip home.

Since the problem is containable by using the internal heater, Im going to suffer it until weekend. Then I'm going to take a look at the thermostat. If the drained water is mankey, I'll take off the rad and flush it through.

It seems Dave Baker & Anthony Britt were both right about the expansion tank cap .....

This afters I called Sunwin Renault Bradford (reputed to be the 'nicest' of the Renault dealers in the north )for a price for a thermostat. The conversation started as I suspected......my model had a sealed unit thermostat which has been superceded by a more usual split design. This meant it would cost me £66+vat for the new body before I even got the stat... I tried it on by explaining the symptom and the guy more or less stopped me in my tracks and said it would be the expansion tank cap. He said, put it this way...we don't sell many thermostats, but we sell loads of tank caps.

Renault sell two types which have different design pressures, a brown one for £3 and a blue one for £8. After thanking him for the advice, I nipped out to my company's car park and took a look at my exp tank. Mine was the cheaper brown variety and I noticed the water level was half and inch above the max. I took off my cap and gave the inside of it a bit of a scientific 'prod'. I only wanted to check because I was going to check with a few mates to see if their Renaults were the same.

Anyhow, clocking off time came and I set off home over the Pennies......the temp spot on all the way home, even when I leathered it on the climb out of Brighouse @ 80+. So it seems that scientific prod did the trick

So when I've got a new £3 cap on Sat morning and drained off a little of that excess coolant, that will be one less worry. Then I can concentrate on its stress corroded power steering pipe, poor starting , injector refurb, high vibration ( IMO..new mounts )

What I failed to comprehend is that I thought the cap was there to keep water in and act as a pressure relief device by bypassing out an overflow. With this system, that overflow is piped back into make thermostat body. It seems this design of cap is supposed to let air in, so its important not to overfill the tank. I still can't get my head around why this would create an overheating problem, but I've just witnessed the change after prodding the cap, so if anyone can explain this to me with the aid if sketches/diagrams it would be welcome.. Thx